The present invention relates to an apparatus and method for spinning polymeric yarn of the type wherein an extruder heats and melts a polymeric material and delivers the resulting melt to a spin head which includes one or more spinnerets. The melt is extruded through each of the spinnerets to form a downwardly advancing bundle of filaments, and the filaments are gathered together to form a yarn which is wound into a package.
A melt spinning apparatus as described above is described, for example, in the detailed conference report on the 33rd International Manmade Fibre Symposium, Dornbirn, 1994, pages 1-11. In this described apparatus, additives, e.g. for ultraviolet stabilization or spin-dyeing, are supplied through an auxiliary extruder to the melt in the main extruder. Feeding of the additives is effected at the end of the main extruder into a dynamic mixer. From there the melt passes through a melt line to a spin head, which comprises an extrusion pump and a spinneret.
In spinning installations, the main extruder simultaneously supplies a plurality of spinnerets of a spin head disposed in a spinning beam. In so doing, the melt is directed from the main extruder to a distributor pump. Such a distributor pump, of the type known from WO 94/19516 and corresponding U.S. Pat. No. 5,637,331, divides the main melt flow into a plurality of individual partial flows and directs each of the latter to a spinneret.
With the known apparatus the problem arises that a change of additives, e.g. a change of color, results in extended non-productive periods for the installation. In order to be able to spin the new grade of yarn, the installation has to be rinsed from the end of the main extruder to the spinning head.
Such spinning installations have the added drawback that the entire spinning installation may simultaneously produce only yarns of a typical melt composition.
It is accordingly an object of the present invention to provide a melt spinning apparatus and method wherein the admixture of the additives may occur as late as possible in the processing sequence of the melt.
A further object of the invention is to design the apparatus and method in such a way that the spinning installation may be operated with the maximum degree of flexibility.